Caryophyllene is a sesquiterpenoid derivative that can be obtained from the oils of a number of plants, such as clove and catmint.
The partial reduction of caryophyllene, or isomers thereof, to their corresponding dihydro forms has been disclosed in several references, U.S. Pat. No. 3,966,819 discloses the photoisomerization of caryophyllene to iso-caryophyllene, and discloses that iso-caryophyllene can be hydrogenated to iso-dihydrocaryophyllene in the presence of a Raney nickel catalyst. Rao and Devaprabhakara [Tetrahedron (1978) 34:2223-2227] describe the partial reduction of caryophyllene and isocaryophyllene with diimide to the dihydro products dihydrocaryophyllene and dihydroisocaryophyllene, respectively.
Several references describe the complete hydrogenation of caryophyllene to the tetrahydro derivative. Naves and Perrottet [“Volatile Plant Materials, XIV, Structure of Caryophyllene”, Helv. Chim. Acta, (1941) 24:789-804] disclose the hydrogenation of caryophyllene to tetrahydrocaryophyllene in the presence of PtO2, which is an unsupported catalyst. Similarly, Sorm et al [Chemistry & Industry (1956) 154-155] disclose the preparation of tetrahydrocaryophyllene by catalytic hydrogenation of caryophyllene with PtO2 in the presence of glacial acetic acid.
A need nevertheless exists for an economically viable route to the synthesis of the hydrogenated forms of caryophyllene.